Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$54.91	9.263%	$59.9963	$60.00	$60.00	$60.00
Purchase #2	$19.39	12.818%	$21.8754	$21.88	$21.90	$21.90
Purchase #3	$95.33	11.610%	$106.3978	$106.40	$106.40	$106.40
Purchase #4	$241.75	4.855%	$253.487	$253.49	$253.50	$253.50
Purchase #5	$42.29	8.710%	$45.9735	$45.97	$45.95	$46.00
Purchase #6	$152.71	12.540%	$171.8598	$171.86	$171.85	$171.90
Purchase #7	$93.95	11.103%	$104.3813	$104.38	$104.40	$104.40
7 purchase totals =	$700.33		$763.9711	$763.98	$764.00	$764.10